Fast precipitation of calcium phosphate layers on titanium induced by simple chemical treatments

Surface Topography Has Less Influence on Peri-Implantitis than Patient Factors: A Comparative Clinical Study of Two Dental Implant Systems

OBJECTIVES

This study aims to assess the risk of peri-implantitis (PI) onset among different implant systems and evaluate the severity of the disease from a population of patients treated in a university clinic. Furthermore, this study intends to thoroughly examine the surface properties of the implant systems that have been identified and investigated.

MATERIAL AND METHODS

Data from a total of six hundred and 14 patients were extracted from the Institute of Clinical Dentistry, Dental Faculty, University of Oslo. Subject- and implant-based variables were collected, including the type of implant, date of implant installation, medical records, recall appointments up to 2022, periodontal measurements, information on diabetes, smoking status, sex, and age. The outcome of interest was the diagnosis of PI, defined as the occurrence of bleeding on probing (BoP), peri-implant probing depth (PD) ≥ 5 mm, and bone loss (BL). Data were analyzed using multivariate linear and logistic regression. Scanning electron microscopy, light laser profilometer, and X-ray photoelectron spectroscopy were utilized for surface and chemical analyses.

RESULTS

Among the patients evaluated, 6.8% were diagnosed with PI. A comparison was made between two different implant systems: Dentsply Sirona, OsseospeedTM and Straumann SLActive, with mean follow-up times of 3.84 years (SE: 0.15) and 3.34 years (SE: 0.15), respectively. The surfaces have different topographies and surface chemistry. However, no significant association was found between PI and implant surface/system, including no difference in the onset or severity of the disease. Nonetheless, plaque control was associated with an increased risk of developing PI, along with the gender of the patient. Furthermore, patients suffering from PI exhibited increased BL in the anterior region.

CONCLUSION

No differences were observed among the evaluated implant systems, although the surfaces have different topography and chemistry. Factors that affected the risk of developing PI were plaque index and male gender. The severity of BL in patients with PI was more pronounced in the anterior region. Consequently, our findings show that success in implantology is less contingent on selecting implant systems and more on a better understanding of patient-specific risk factors, as well as on implementing biomaterials that can more effectively debride dental implants.

In situ fabrication of cerium-incorporated hydroxyapatite/magnetite nanocomposite coatings with bone regeneration and osteosarcoma potential

With the ultimate goal of providing a novel platform able to inhibit bacterial adhesion, biofilm formation, and anticancer properties, cerium-doped hydroxyapatite films enhanced with magnetite were developed via spin-coating. The unique aspect of the current study is the potential for creating cerium-doped hydroxyapatite/Fe3O4 coatings on a titanium support to enhance the functionality of bone implants. To assure an increase in the bioactivity of the titanium surface, alkali pretreatment was done before deposition of the apatite layer. Scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD) analysis, and Fourier transform-infrared (FTIR) spectroscopy were used to evaluate coatings. Coatings demonstrated good efficacy against Staphylococcus aureus and Escherichia coli, with the latter showing the highest efficacy. In vitro bioactivity in simulated body fluid solution showed this material to be proficient for bone-like apatite formation on the implant surface. Electrochemical impedance spectroscopy was undertaken on intact coatings to examine the barrier properties of composites. We found that spin-coating at 4000 rpm could greatly increase the total resistance. After seeding with osteoblastic populations, Ce-HAP/Fe3O4 materials the adhesion and proliferation of cells. The heating capacity of the Ce-HAP/Fe3O4 film was optimal at 45 °C at 15 s at a frequency of 318 kHz. Osseointegration depends on many more parameters than hydroxyapatite production, so these coatings have significant potential for use in bone healing and bone-cancer therapy.

There Are over 60 Ways to Produce Biocompatible Calcium Orthophosphate (CaPO4) Deposits on Various Substrates

A The present overview describes various production techniques for biocompatible calcium orthophosphate (abbreviated as CaPO4) deposits (coatings, films and layers) on the surfaces of various types of substrates to impart the biocompatible properties for artificial bone grafts. Since, after being implanted, the grafts always interact with the surrounding biological tissues at the interfaces, their surface properties are considered critical to clinical success. Due to the limited number of materials that can be tolerated in vivo, a new specialty of surface engineering has been developed to desirably modify any unacceptable material surface characteristics while maintaining the useful bulk performance. In 1975, the development of this approach led to the emergence of a special class of artificial bone grafts, in which various mechanically stable (and thus suitable for load-bearing applications) implantable biomaterials and artificial devices were coated with CaPO4. Since then, more than 7500 papers have been published on this subject and more than 500 new publications are added annually. In this review, a comprehensive analysis of the available literature has been performed with the main goal of finding as many deposition techniques as possible and more than 60 methods (double that if all known modifications are counted) for producing CaPO4 deposits on various substrates have been systematically described. Thus, besides the introduction, general knowledge and terminology, this review consists of two unequal parts. The first (bigger) part is a comprehensive summary of the known CaPO4 deposition techniques both currently used and discontinued/underdeveloped ones with brief descriptions of their major physical and chemical principles coupled with the key process parameters (when possible) to inform readers of their existence and remind them of the unused ones. The second (smaller) part includes fleeting essays on the most important properties and current biomedical applications of the CaPO4 deposits with an indication of possible future developments.

Surface analysis of (Ti,Mg)N coated bone fixation devices following the rabbit femur surgery

BACKGROUND

Magnesium (Mg) enhances the bone regeneration, mineralization and attachment at the tissue/biomaterial interface.

OBJECTIVE

In this study, the effect of Mg on mineralization/osseointegration was determined using (Ti,Mg)N thin film coated Ti6Al4V based plates and screws in vivo.

METHODS

TiN and (Ti,Mg)N coated Ti6Al4V plates and screws were prepared using arc-PVD technique and used to fix rabbit femur fractures for 6 weeks. Then, mineralization/osseointegration was assessed by surface analysis including cell attachment, mineralization, and hydroxyapatite deposition on concave and convex sides of the plates along with the attachment between the screw and the bone.

RESULTS

According to Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) analyses; cell attachment and mineralization were higher on the concave sides of the plates from both groups in comparison to the convex sides. However, mineralization was significantly higher on Mg-containing ones. The mean gray value indicating mineralized area after von Kossa staining was found as 0.48 ± 0.01 and 0.41 ± 0.04 on Mg containing and free ones respectively. Similarly, Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) analyses showed that hydroxyapatite growth was abundant on the Mg-containing and concave sides of the plates. Enhanced mineralization and strong attachment to bone were also detected in EDS and SEM analyses of Mg-containing screws.

CONCLUSION

These findings indicated that (Ti,Mg)N coatings can be used to increase attachment at the implant tissue interface due to accelerated mineralization, cell attachment, and hydroxyapatite growth.

Is There a Better Biomaterial for Dental Implants than Titanium?—A Review and Meta-Study Analysis

This article focuses on preclinical studies and reviews the available evidence from the literature on dental implant and abutment materials in the last decade. Specifically, different peri-implantitis materials and how surface modifications may affect the peri-implant soft-tissue seal and subsequently delay or hinder peri-implantitis are examined. This review analyzed more than 30 studies that were Randomized Controlled Trials (RCTs), Controlled Clinical Trials (CCTs), or prospective case series (CS) with at least six months of follow-up. Meta-analyses were performed to make a comparison between different implant materials (titanium vs. zirconia), including impact on bone changes, probing depth, plaque levels, and peri-implant mucosal inflammation, as well as how the properties of the implant material and surface modifications would affect the peri-implant soft-tissue seal and peri-implant health conditions. However, there was no clear evidence regarding whether titanium is better than other implant materials. Clinical evidence suggests no difference between different implant materials in peri-implant bone stability. The metal analysis offered a statistically significant advantage of zirconia implants over titanium regarding developing a favorable response to the alveolar bone.

Improvement of osseointegration of Ti–6Al–4V ELI alloy orthodontic mini-screws through anodization, cyclic pre-calcification, and heat treatments

Background

Mini-screws are widely used as temporary anchorages in orthodontic treatment, but have the disadvantage of showing a high failure rate of about 10%. Therefore, orthodontic mini-screws should have high biocompatibility and retention. Previous studies have demonstrated that the retention of mini-screws can be improved by imparting bioactivity to the surface. The method for imparting bioactivity proposed in this paper is to sequentially perform anodization, periodic pre-calcification, and heat treatments with a Ti–6Al–4V ELI alloy mini-screw.

Materials and methods

A TiO2 nanotube-structured layer was formed on the surface of the Ti–6Al–4V ELI alloy mini-screw through anodization in which a voltage of 20 V was applied to a glycerol solution containing 20 wt% H2O and 1.4 wt% NH4F for 60 min. Fine granular calcium phosphate precipitates of HA and octacalcium phosphate were generated as clusters on the surface through the cyclic pre-calcification and heat treatments. The cyclic pre-calcification treatment is a process of immersion in a 0.05 M NaH2PO4 solution and a saturated Ca(OH)2 solution at 90 °C for 1 min each.

Results

It was confirmed that the densely structured protrusions were precipitated, and Ca and P concentrations, which bind and concentrate endogenous bone morphogenetic proteins, increased on the surface after simulated body fluid (SBF) immersion test. In addition, the removal torque of the mini-screw fixed into rabbit tibias for 4 weeks was measured to be 8.70 ± 2.60 N cm.

Conclusions

A noteworthy point in this paper is that the Ca and P concentrations, which provide a scaffold suitable for endogenous bone formation, further increased over time after SBF immersion of the APH group specimens. The other point is that our mini-screws have a significantly higher removal torque compared to untreated mini-screws. These results represent that the mini-screw proposed in this paper can be used as a mini-screw for orthodontics.

Approaches to promoting bone marrow mesenchymal stem cell osteogenesis on orthopedic implant surface

Bone marrow-derived mesenchymal stem cells (BMSCs) play a critical role in the osseointegration of bone and orthopedic implant. However, osseointegration between the Ti-based implants and the surrounding bone tissue must be improved due to titanium’s inherent defects. Surface modification stands out as a versatile technique to create instructive biomaterials that can actively direct stem cell fate. Here, we summarize the current approaches to promoting BMSC osteogenesis on the surface of titanium and its alloys. We will highlight the utilization of the unique properties of titanium and its alloys in promoting tissue regeneration, and discuss recent advances in understanding their role in regenerative medicine. We aim to provide a systematic and comprehensive review of approaches to promoting BMSC osteogenesis on the orthopedic implant surface.

Native Osseous CaP Biomineral Coating on a Biomimetic Multi-Spiked Connecting Scaffold Prototype for Cementless Resurfacing Arthroplasty Achieved by Combined Electrochemical Deposition

The multi-spiked connecting scaffold (MSC-Scaffold) prototype with spikes mimicking the interdigitations of articular subchondral bone is an essential innovation in surgically initiated fixation of resurfacing arthroplasty (RA) endoprosthesis components. This paper aimed to present a determination of the suitable range of conditions for the calcium phosphate (CaP) potentiostatic electrochemical deposition (ECD_V=const) on the MSC-Scaffold prototype spikes to achieve a biomineral coating with a native Ca/P ratio. The CaP ECD_V=const process on the MSC-Scaffold Ti4Al6V pre-prototypes was investigated for potential V_ECDfrom −9 to −3 V, and followed by 48 h immersion in a simulated body fluid. An acid–alkaline pretreatment (AAT) was applied for a portion of the pre-prototypes. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) studies of deposited coatings together with coatings weight measurements were performed. Themost suitable V_ECD range, from −5.25 to −4.75 V, was determined as the native biomineral Ca/P ratio of coatings was achieved. AAT increases the weight of deposited coatings (44% for V_ECD = −5.25 V, 9% for V_ECD = −5.00 V and 15% for V_ECD = −4.75 V) and the coverage degree of the lateral spike surfaces (40% for V_ECD = −5.25 V, 14% for V_ECD = −5.00 V and 100% for V_ECD = −4.75 V). XRD confirmed that the multiphasic CaP coating containing crystalline octacalcium phosphate is produced on the lateral surface of the spikes of the MSC-Scaffold. ECD_V=const preceded by AAT prevents micro-cracks on the bone-contacting surfaces of the MSC-Scaffold prototype, increases its spikes’ lateral surface coverage, and results in the best modification effect at V_ECD = −5.00 V. To conclude, the biomimetic MSC-Scaffold prototype with desired biomineral coating of native Ca/P ratio was obtained for cementless RA endoprostheses.

Biomimetic Mineralization of Biomaterials Using Simulated Body Fluids for Bone Tissue Engineering and Regenerative Medicine<sup/>

Development of synthetic biomaterials imbued with inorganic and organic characteristics of natural bone that are capable of promoting effective bone tissue regeneration is an ongoing goal of regenerative medicine. Calcium phosphate (CaP) has been predominantly utilized to mimic the inorganic components of bone, such as calcium hydroxyapatite, due to its intrinsic bioactivity and osteoconductivity. CaP-based materials can be further engineered to promote osteoinductivity through the incorporation of osteogenic biomolecules. In this study, we briefly describe the microstructure and the process of natural bone mineralization and introduce various methods for coating CaP onto biomaterial surfaces. In particular, we summarize the advantages and current progress of biomimetic surface-mineralizing processes using simulated body fluids for coating bone-like carbonated apatite onto various material surfaces such as metals, ceramics, and polymers. The osteoinductive effects of integrating biomolecules such as proteins, growth factors, and genes into the mineral coatings are also discussed.

Calcium orthophosphate deposits: Preparation, properties and biomedical applications

Since various interactions among cells, surrounding tissues and implanted biomaterials always occur at their interfaces, the surface properties of potential implants appear to be of paramount importance for the clinical success. In view of the fact that a limited amount of materials appear to be tolerated by living organisms, a special discipline called surface engineering was developed to initiate the desirable changes to the exterior properties of various materials but still maintaining their useful bulk performances. In 1975, this approach resulted in the introduction of a special class of artificial bone grafts, composed of various mechanically stable (consequently, suitable for load bearing applications) implantable biomaterials and/or bio-devices covered by calcium orthophosphates (CaPO4) to both improve biocompatibility and provide an adequate bonding to the adjacent bones. Over 5000 publications on this topic were published since then. Therefore, a thorough analysis of the available literature has been performed and about 50 (this number is doubled, if all possible modifications are counted) deposition techniques of CaPO4 have been revealed, systematized and described. These CaPO4 deposits (coatings, films and layers) used to improve the surface properties of various types of artificial implants are the topic of this review.

Bioactive Ti alloy with hydrophilicity, antibacterial activity and cytocompatibility

Schematic representation of Ti64 alloy with antibacterial activity, bioactivity and cell compatibility.

The use of physiological solutions or media in calcium phosphate synthesis and processing

This review examined the literature to spot uses, if any, of physiological solutions/media for the in situ synthesis of calcium phosphates (CaP) under processing conditions (i.e. temperature, pH, concentration of inorganic ions present in media) mimicking those prevalent in the human hard tissue environments. There happens to be a variety of aqueous solutions or media developed for different purposes; sometimes they have been named as physiological saline, isotonic solution, cell culture solution, metastable CaP solution, supersaturated calcification solution, simulated body fluid or even dialysate solution (for dialysis patients). Most of the time such solutions were not used as the aqueous medium to perform the biomimetic synthesis of calcium phosphates, and their use was usually limited to the in vitro testing of synthetic biomaterials. This review illustrates that only a limited number of research studies used physiological solutions or media such as Earle's balanced salt solution, Bachra et al. solutions or Tris-buffered simulated body fluid solution containing 27mM HCO3(-) for synthesizing CaP, and these studies have consistently reported the formation of X-ray-amorphous CaP nanopowders instead of Ap-CaP or stoichiometric hydroxyapatite (HA, Ca10(PO4)6(OH)2) at 37°C and pH 7.4. By relying on the published articles, this review highlights the significance of the use of aqueous solutions containing 0.8-1.5 mMMg(2+), 22-27mM HCO3(-), 142-145mM Na(+), 5-5.8mM K(+), 103-133mM Cl(-), 1.8-3.75mM Ca(2+), and 0.8-1.67mM HPO4(2-), which essentially mimic the composition and the overall ionic strength of the human extracellular fluid (ECF), in forming the nanospheres of X-ray-amorphous CaP.

Cathodic Polarization Coats Titanium Based Implant Materials with Enamel Matrix Derivate (EMD)

The idea of a bioactive surface coating that enhances bone healing and bone growth is a strong focus of on-going research for bone implant materials. Enamel matrix derivate (EMD) is well documented to support bone regeneration and activates growth of mesenchymal tissues. Thus, it is a prime candidate for coating of existing implant surfaces. The aim of this study was to show that cathodic polarization can be used for coating commercially available implant surfaces with an immobilized but functional and bio-available surface layer of EMD. After coating, XPS revealed EMD-related bindings on the surface while SIMS showed incorporation of EMD into the surface. The hydride layer of the original surface could be activated for coating in an integrated one-step process that did not require any pre-treatment of the surface. SEM images showed nano-spheres and nano-rods on coated surfaces that were EMD-related. Moreover, the surface roughness remained unchanged after coating, as it was shown by optical profilometry. The mass peaks observed in the matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS) analysis confirmed the integrity of EMD after coating. Assessment of the bioavailability suggested that the modified surfaces were active for osteoblast like MC3M3-E1 cells in showing enhanced Coll-1 gene expression and ALP activity.

Increased reactivity and in vitro cell response of titanium based implant surfaces after anodic oxidation

In the quest for improved bone growth and attachment around dental implants, chemical surface modifications are one possibility for future developments. The biological properties of titanium based materials can be further enhanced with methods like anodic polarization to produce an active rather than a passive titanium oxide surface. Here we investigate the formation of hydroxide groups on sand blasted and acid etched titanium and titanium-zirconium alloy surfaces after anodic polarization in an alkaline solution. X-ray photoelectron spectroscopy shows that the activated surfaces had increased reactivity. Furthermore the activated surfaces show up to threefold increase in OH(-) concentration in comparison to the original surface. The surface parameters Sa, Sku, Sdr and Ssk were more closely correlated to time and current density for titanium than for titanium-zirconium. Studies with MC3T3-E1 osteoblastic cells showed that OH(-) activated surfaces increased mRNA levels of osteocalcin and collagen-I.

Effect of cyclic precalcification of nanotubular TiO2 layer on the bioactivity of titanium implant

The objective of this study is to investigate the effect of cyclic precalcification treatment to impart bioactive properties for titanium implants. Before precalcification, the titanium implants were subjected to blasting using hydroxyapatite (HAp), a resorbable blasting medium (RBM treated), and anodized using an electrolyte containing glycerol, H₂O, and NH₄F. Precalcification treatment was performed by two different methods, namely, continuous immersion treatment (CIT) and alternate immersion treatment (AIT). In CIT, the RBM treated and anodized titanium implants were immersed in 0.05 M NaH₂PO₄ solution at 80°C and saturated Ca(OH)₂ solution at 100°C for 20 min, whereas during AIT, they were immersed alternatively in both solutions for 1 min for 20 cycles. Anodizing of the titanium implants enables the formation of self-organized TiO₂ nanotubes. Cyclic precalcification treatment imparts a better bioactive property and enables an increase in activation level of the titanium implants. The removal torque values of the RBM treated, CIT treated, and AIT treated titanium implants are 10.8 ± 3.7 Ncm, 17.5 ± 3.5 Ncm, and 28.1 ± 2.4 Ncm, respectively. The findings of the study indicate the cyclic precalcification in an effective surface treatment method that would help accelerate osseointegration and impart bioactive property of titanium implants.

Interaction between mesenchymal stem cells and Ti-30Ta alloy after surface treatment

In this study, in vitro cytocompatibility was investigated in the Ti-30Ta alloy after two kinds of surfaces treatments: alkaline and biomimetic treatment. Each condition was evaluated by scanning electron microscopy/energy-dispersive X-ray spectroscopy. Cellular adhesion, viability, protein expression, morphology, and differentiation were evaluated with Bone marrow stromal cells (MSCs) to investigate the short and long-term cellular response by fluorescence microscope imaging and colorimetric assays techniques. Two treatments exhibited similar results with respect to total protein content and enzyme activity as compared with alloy without treatment. However, it was observed improved of the biomineralization, bone matrix formation, enzyme activity, and MSCs functionality after biomimetic treatment. These results indicate that the biomimetic surface treatment has a high potential for enhanced osseointegration.

Conformation change of bovine serum albumin induced by bioactive titanium metals and its effects on cell behaviors

The conformation change of bovine serum albumin (BSA) induced by bioactive titanium surfaces, including acid-alkali-treated titanium (AA-Ti) and alkali-heat-treated titanium (AH-Ti), was studied, and its effects on the activity of MC3T3-E1 cell were evaluated. Pure titanium metal (P-Ti) was used as control. The AA-Ti could adsorb more BSA on its surface than AH-Ti and P-Ti. The α-helix part of the protein adsorbed on P-Ti has weakly decreased compared with native BSA, and it dramatically decreased on AA-Ti and AH-Ti. The β-sheet segment of proteins adsorbed on P-Ti and AH-Ti had obviously increased. Much more tryptophan residues were exposed after the protein conformation changed when it interacted with AH-Ti, and some tryptophan residues were enveloped after it interacted with AA-Ti and P-Ti. AA-Ti has more tryptophan residues enveloped than P-Ti. All titanium surfaces induced tyrosine residues exposed, especially for the P-Ti. The higher ratio of COO(-)/NH3(+) for the proteins on P-Ti and AA-Ti indicated an orientation of proteins on P-Ti and AA-Ti, which makes more COO(-) exposed. The lower ratio of COO(-)/NH3(+) on AH-Ti indicates that more NH3(+) is exposed on its surface. The cell proliferation ability on different treated titanium surfaces coated with BSA followed by the order: P-Ti > AA-Ti > AH-Ti, which indicated that the protein conformation change on different bioactive titanium surfaces has great effect on the cell activity. Our results showed that the different biological response of bioactive titanium metals might depend on the protein conformation change induced by the surface structure.

Simvastatin-activated implant surface promotes osteoblast differentiation in vitro

The bone growth promoting effects of statins suggest that these bioactive molecules can be used to improve the integration of bone-anchored implants. This study aimed at the application of simvastatin with dental implants for use in patients with low bone density. Coin-shaped titanium zirconium samples with grit-blasted and acid-etched surface were coated with simvastatin, using a novel anodic oxidation setup under alkaline conditions. The presence of intact simvastatin attached to the surface was confirmed by infrared spectroscopy. A binding site on the aliphatic O-H group was discovered and the integration of (1)H, (18)O and (12)C in the depth of the surface were observed by secondary ion mass spectroscopy. A simvastatin concentration of about 60 g/cm(2) was found in a release study over 72 h. The simvastatin-coated surfaces promoted alkaline phosphatase, collagen type I and osteocalcin gene expression of MC3T3-E1 cells. This suggested that the demonstrated coating holds potential for use in patients with compromised bone.

An efficient biomimetic coating methodology for a prosthetic alloy

The combination of the load-bearing metallic implants with the bioactive materials in the design of synthetic implants is an important aspect in the biomaterials research. Biomimetic coating of bioinert alloys with calcium phosphate phases provides a good alternative to the prerequisite for the continual replacement of implants because of the failure of bone-implant integration. We attempted to accelerate the biomimetic coating process of stainless steel alloy (316L) with biomimetic apatite. In addition, we investigated the incorporation of functioning minerals such as strontianite and smithsonite into the deposited layer. In order to develop a highly mature apatite coating, our method requires soaking of the pre-treated alloy in highly concentrated synthetic body fluid for only few hours. Surface characterizations were performed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). Also, the deposited apatitic layers were analysed by powder diffraction X-ray analysis (XRD). 316L surface showed the growth of highly crystalline, low carbonated hydroxyapatite, after only 6h of the whole soaking process.

Calcium orthophosphate coatings, films and layers

In surgical disciplines, where bones have to be repaired, augmented or improved, bone substitutes are essential. Therefore, an interest has dramatically increased in application of synthetic bone grafts. As various interactions among cells, surrounding tissues and implanted biomaterials always occur at the interfaces, the surface properties of the implants are of the paramount importance in determining both the biological response to implants and the material response to the physiological conditions. Hence, a surface engineering is aimed to modify both the biomaterials, themselves, and biological responses through introducing desirable changes to the surface properties of the implants but still maintaining their bulk mechanical properties. To fulfill these requirements, a special class of artificial bone grafts has been introduced in 1976. It is composed of various mechanically stable (therefore, suitable for load bearing applications) biomaterials and/or bio-devices with calcium orthophosphate coatings, films and layers on their surfaces to both improve interactions with the surrounding tissues and provide an adequate bonding to bones. Many production techniques of calcium orthophosphate coatings, films and layers have been already invented and new promising techniques are continuously investigated. These specialized coatings, films and layers used to improve the surface properties of various types of artificial implants are the topic of this review.

Effects of osteogenic growth factors on bone marrow stromal cell differentiation in a mineral-based delivery system

Delivering growth factors from bone-like mineral combines osteoinductivity with osteoconductivity. The effects of individual and sequential exposure of BMP-2 and FGF-2 on osteogenic differentiation, and their release from apatite were studied to design a dual delivery system. Bone marrow stromal cells were seeded on TCPS with the addition of FGF-2 (2.5, 10, 40 ng/ml) or BMP-2 (50, 150, 450 ng/ml) for 6 days. DNA content and osteogenic response were examined weekly for 3 weeks. FGF-2 increased DNA content; however, high concentrations of FGF-2 inhibited/delayed osteogenic differentiation, while a threshold concentration of BMP-2 was required for significant osteogenic enhancement. The sequence of delivery of BMP-2 (300 ng/ml) and FGF-2 (2.5 ng/ml) also had a significant impact on osteogenic differentiation. Delivery of FGF-2 followed by BMP-2 or delivery of BMP-2 followed by BMP-2 and FGF-2 enhanced osteogenic differentiation compared to the simultaneous delivery of both factors. Release of BMP-2 and FGF-2 from bone-like mineral was significantly affected by the concentration used during coprecipitation. BMP-2 also demonstrated a higher "burst" release compared to FGF-2. By integrating the results of the sequential delivery of BMP-2 and FGF-2 in solution, with the release of individual growth factors from mineral, an organic/inorganic delivery system based on coprecipitation can be designed for multiple biomolecules.

Surface characterization and biological response of carbon-coated oxygen-diffused titanium having different topographical surfaces

The materials (C-ODTi) with different topographical surfaces that possess interstitial oxygen atoms into the host titanium lattice and an upper nanometric surface layer of anatase-TiO(2) covered by a carbon thin layer were fabricated in this study. The carbon thin layer on the surface of C-ODTi was composed of amorphous carbon and nano-graphite crystals. In vitro tests, using human bone marrow-derived mesenchymal cells (hBMCs), were performed to check cytotoxicity, examining in particular cell morphology, cell proliferation, cell differentiation, and mineralization capability. After 10 days of culture a higher degree of cell viability was observed on the surface of C-ODTi with an abraded surface. We also observed that hBMCs cultured in direct contact with C-ODTi maintained their capability to express alkaline phosphatase activity (ALP) and formed mineralized nodules similar to the control cultures. Our results demonstrate that the carbon layer coating on the surface of C-ODTi possess better biological response than commercially pure titanium (cp Ti), which was evidenced by the higher proliferation rates of osteoblasts, higher osteo-differentiation and a higher mineralization capability.

Anti-inflammatory properties of bioactive titanium metals

Anti-inflammatory properties of bioactive titanium metals prepared by anodic oxidation (AO-Ti) and alkali-heat (AH-Ti) treatments were studied by bacterial adhesion test and myeloperoxidase (MPO) activity assay methods. The bioactivities of the metals were also evaluated by apatite formation ability and osteoblasts culture experiments. Both metals could induce apatite formation and support osteoblasts proliferation. At the condition with normal incandescent light shine, both bioactive titanium metals had antibacterial adhesion properties compared with the titanium metal without treatment. The MPO activity assay proved that they both showed anti-inflammatory properties in vivo. The bioactive AO-Ti had better anti-inflammatory properties than the AH-Ti. It indicated that it is possible to optimize the anti-inflammatory properties of the bioactive titanium metals by different preparation methods.

Controlled electro-implementation of fluoride in titanium implant surfaces enhances cortical bone formation and mineralization

Previous studies have shown that bone-to-implant attachment of titanium implants to cortical bone is improved when the surface is modified with hydrofluoric acid. The aim of this study was to investigate if biological factors are involved in the improved retention of these implants. Fluoride was implemented in implant surfaces by cathodic reduction with increasing concentrations of HF in the electrolyte. The modified implants were placed in the cortical bone in the tibias of New Zealand white rabbits. After 4 weeks of healing, wound fluid collected from the implant site showed lower lactate dehydrogenase activity and less bleeding in fluoride-modified implants compared to control. A significant increase in gene expression levels of osteocalcin and tartrate-resistant acid phosphatase (TRAP) was found in the cortical bone attached to Ti implants modified with 0.001 and 0.01 vol.% HF, while Ti implants modified with 0.1% HF showed only induced TRAP mRNA levels. These results were supported by the performed micro-CT analyses. The volumetric bone mineral density of the cortical bone hosting Ti implants modified with 0.001% and 0.01% HF was higher both in the newly woven bone (<100 microm from the interface) and in the older Haversian bone (>100 microm). In conclusion, the modulation of these biological factors by surface modification of titanium implants with low concentrations of HF using cathodic reduction may explain their improved osseointegration properties.

Fabrication and characterization of oxygen-diffused titanium for biomedical applications

Although titanium has been successful as an orthopedic or dental implant material, performance problems still persist concerning implant-bone interfacial bonding strength. In this study a novel oxygen-diffused titanium (ODTi), fabricated by introducing oxygen into the titanium crystal lattice by thermal treatment, was investigated. The fabricated material is the result of a surface modification made on commercially pure titanium (cp Ti) previously coated with poly(vinyl alcohol) (PVA) by means of a thermal treatment performed at 700 degrees C in an ultra-pure argon atmosphere. The thermal treatment at 700 degrees C led to the formation of an anatase TiO(2) film on the cp Ti surface and a concentration gradient of oxygen into titanium. The surface of the fabricated ODTi consisted of an outer nanometric layer of anatase TiO(2) and an inner nanometric layer of Ti(2)O(x) (x<1) in which the oxygen is in solid solution with the titanium metal. It was found that ODTi possesses in vitro apatite formation ability after being soaked into simulated body fluid (SBF) solution. This apatite formation ability is attributed to the presence of the anatase TiO(2) outermost surface layer and to abundant hydroxyl groups (-OH) formed on the ODTi surface after immersion in SBF.

Gene delivery via DNA incorporation within a biomimetic apatite coating

Integrating inductivity with conductivity in a material may advance tissue engineering. An organic/inorganic hybrid was developed by incorporating plasmid DNA encoding for the beta-gal gene complexed with Lipofectamine 2000 (DNA-Lipoplex) within apatite via coprecipitation. It was hypothesized that this system will result in enhanced transfection efficiency compared to DNA-Lipoplexes adsorbed to the mineral surface and DNA coprecipitated without Lipofectamine 2000. PLGA films were cast onto glass slips and apatite and DNA were coprecipitated in modified simulated body fluid (mSBF). DNA-Lipoplex presence in mineral, DNA-Lipoplex stability (vs. coprecipitation time), and transfection efficiency (determined with C3H10T1/2 cells) as a function of coprecipitation time, DNA-Lipoplex concentration, and DNA incorporation method were studied. DNA-Lipoplex presence and spatial distribution on apatite were confirmed through fluorescence. Transfection efficiency was highest for 6h of DNA-Lipoplex coprecipitation. Differences in transfection efficiency were found between the DNA concentrations, with the highest efficiency for coprecipitation being 40 microg/ml (p < or = 0.009 relative to other coprecipitation concentrations). Significant differences in transfection efficiency existed between incorporation methods (p < 0.05) with the highest efficiency for DNA-Lipoplex coprecipitation. This hybrid material system not only integrates inductivity provided by the DNA and conductivity provided by the apatite, but it also has significant implications in non-viral gene delivery due to its ability to increase transfection efficiency.

Influence of calcium ion deposition on apatite-inducing ability of porous titanium for biomedical applications

In the present study, the influence of calcium ion deposition on the apatite-inducing ability of porous titanium (Ti) was investigated in a modified simulated body fluid (m-SBF). Calcium hydroxide (Ca(OH)(2)) solutions with five degrees of saturation were used to hydrothermally deposit Ca ions on porous Ti with a porosity of 80%. Apatite-inducing ability of the Ca-ion-deposited porous Ti was evaluated by soaking them in m-SBF for up to 14 days. Scanning electron microscopy (SEM) and X-ray diffractometry (XRD) confirmed that a thin layer of calcium titanate (CaTiO(3))/calcium oxide (CaO) mixture with a nanostructured porous network was produced on porous Ti substrates after hydrothermal treatment at 200 degrees C for 8 h. X-ray photoelectron spectroscopy results demonstrated that the content of the Ca ions deposited on Ti and the thickness of the CaTiO(3)/CaO layer increased with increasing saturation degree of the Ca(OH)(2) solution. The thickest (over 10 nm) CaTiO(3)/CaO layer with the highest Ca content was achieved on the Ti treated in an oversaturated Ca(OH)(2) solution (0.2 M). SEM, XRD, transmission electron microscopy and Fourier transformed infrared spectroscopy analysis indicated that the porous Ti samples deposited with the highest content of Ca ions exhibited the best apatite-inducing ability, producing a dense and complete carbonated apatite coating after a 14 day soaking in m-SBF. The present study illustrated the validity of using Ca ion deposition as a pre-treatment to endow desirable apatite-inducing ability of porous Ti for bone tissue engineering applications.

Formation of hydroxyapatite coating using novel chemo-biomimetic method

A novel chemo-biomimetic method was developed to deposit hydroxyapatite (HA), simulating the porous nano-scale structure and chemical composition of natural bone. Electrochemical activation in NaOH solution, a prerequisite process to heterogeneously nucleate hydroxyapatite in this investigation, creates nano-scale porous structure on the surface of Ti6Al4V alloy. XPS analysis confirmed that the surface of activated Ti6Al4V substrate converted to TiO2 during activation, existing in the form of hydrated TiO2. Benefiting from the biocompatible top-layer of hydrated TiO2 and the favorable alkaline surface chemistry created through the electrochemical activation, the HA coating nucleates heterogeneously and grows continuously on the activated substrate resembling the nano-scale porous bone-like structure. The coating was characterized using XRD, SEM/FESEM/EDX, TEM and FTIR, and was confirmed as pure hydroxyapatite. A coating thickness of 50 microm was achieved, which is preferable and acceptable for medical implant application to promote bone ingrowth, thus enhancing fixation and biocompatibility of implant surface.